The perfect geek material

I never like wood, but I thought it was the only material that you can custom in your garage. Over the years I have a circular saw to cut 2"x4" beams for play things, now the saw is being recalled. I also have a little power sander to smooth the coarse wood so as for the surface not to be too tough for the touch. I once brought a jigsaw to build a custom corner table. I thought it was good but it got thrown away. An fake antique table replaced it.

I was looking for something to replace the cardbox in the yard, when I come across acrylic. I thought it was perfect. It's look like glass, lighter but tougher. And you can cut it to size with a knife. Perfect, just what I needed. So I designed a rather complicated box with lots of compartments, doors and openings in it, using a free CAD package.

I fit my design into a 2'x4' flat piece of acrylic at 1/8" thick. When the piece comes, it was perfect. It really looks good, crystal clear. It was protected by plastic film so you cannot scratch it while cutting it. The thickness is just right. It's just tough for you to build a strong box. Any thicker cost a lot more, and any thinner it feels plastic instead of glass. But there's one catch. There's no way you can cut it with a knife, at least not a decent long edge.

So I brought out my jigsaw. It's tough work. It's very slow to cut through the acrylic compared to wood that is a lot thicker, which is expected. Also, you cannot make a straight cut with a jigsaw, unless you have a decent work bench, which I don't. I should have ordered custom cutting which is more expensive than the material itself. At least for the long cuts, I should use some help. But I soldiered on.

The good thing is that, at a right saw speed, the blade create just enough heat to melt through the acrylic, but not too much melting, giving a nice smooth edge. The saw dust are basically acrylic melted into tiny beads. It's everywhere but a lot more pleasant than wood dust and it's much easy to clean.

The bad - the unexpected jigsaw instead of a knife leaves me with rectangles big and small, all without straight edges and right angles! I know it would be a challenge to fit the pieces together. Also, the dimensions are more than 1/8" off after cutting. So I have to run through the CAD package to made alterations as I went along.

Luckily I brought some small right angled wedges to help to glue the pieces together at the corner, and some squared tubes to help with the squareness of my box. And I settled for some toxic solvents for a quick welding of the pieces, instead of using slow solvents and requiring clamps that I don't have, and don't know how to apply in small spaces.

You can imagine the final box is comparable to a cardboard box using coarse tapes to stick the pieces together. But acrylic is something. You can see the glue, it's clear but there are bubbles in it. It's hard not to use excessive glue for the uneven pieces. It drys hard and visible, but it's as clear as the acrylic. Basically it's just acrylic melted and reformed. The wedges at the corners are ugly, no sides are straight and barely square. No edges are smooth.

But the whole junk is rather addictive to look at. It's my junk and it's like glass suspending in glass. You got to enjoy the fine details, like uneven application of the glues on the edges and hinges. The curved edges, and the blurred edges just like glass. Best of all, it's tough and highly functional. If I order custom cutting for the large pieces, or invest in a bench saw, it would be perfect the 2nd time round.

I can imagine 1/16" thick sheets will be perfect for delicate things, such as custom electronic enclosures. You should be able to cut it accurately using knifes. Polish the edges and use thin glues that make perfect invisible joints. You can drill small accurate holes, or cut out large portions for a screen mount etc. You can order custom laser cutting for you name to stick on it too.

The major problem I had was needing a lot of motors with gearboxes to mount on my beautiful junk. It's just too expensive compared to the whole box, and looked ugly. You can get bare motors a lot cheaper, compact and powerful. But without gears and crank arms they are useless. So after exhausting the web to find something suitable, I cut a little piece of acrylic as the crank arm and drill a hole in it. I put the bare motor shaft in it and glue them together using gorilla glue. It surprised me that now it's a very tough crank arm! The rest of the problem is mounting the motor onto the box. It just need another small piece and screws to clamp the motor securely in place. Now even the motor mount and the crank arm are transparent and look good, with screw suspending in mid air.

I fell in love.

Reliable precision vacation automatic dog feeder and waterer 2

With a little time, my feeder has improved a great deal. I found out by accident that corrugated cardboard box can be treated like wood. You can screw them, bolt them and nut them, glue them, tie them, and best of all, they comes in with most mail orders over the Internet.

Now the feeder is almost like my original simple vision. Find or make a box that is large enough to hold one meal. Use the side with the smallest dimension as the door. Drill two hold to mount the motor, using small bolts and nuts. My toy motor kit comes with a gear box that can mount a rotating arm. The arm is used to keep the door shut. When the motor rotates, the arm rotates away and opens the door for the dry food to drop down. You can drop down a tray of wet food too.

The rest you need is a 7 day timer to turn on the dc adaptor, which in turn drives the motor for a minute. For each day (or meal) you need three components, box with motor, dc adaptor and timer. They work independently so it's highly reliable. There's no single point of failure. And unlike commercial ones that uses a single "valve" to move the dog food, my design allows you to put whatever you want into the box precisely - medicine, treats for different days of the week.

I mount the boxes near the top of a large cardboard box, and tie the large box to garden furniture. There is no mess as the food will not drop outside of the large box, and the dog can't possibly move the box tied to something heavy.

There are plenty of automatic waterers, basically like the toilet tank that will automatically fill themselves and shut off when full. But the commercial ones are far too small, and far too expensive compared to the toilet flush valve.

I was looking to build something to mount a small float valve when I found something better. It was a float valve designed for cattle. I just mount it on a bucket with the supplied hardware and attach a garden hose to it. The large volume in the bucket acts as a large dead weight so I don't need to fix it to anything. Even if the water supply is cut off, the bucketful can last for days.

Now it may be getting even better and more interesting. I'm going to build a reliable circuit so I can get rid of the adapters and the timers. There will only be one power supply, which can be AC indoors, DC outdoors or battery operated. Before that it's a bit daunting to set up all the timers and adapters and boxes.

Nowadays it's amazing with the net. You get electronic components from 1 to 1 million over the Internet, and you are welcomed the same. And there's the online datasheets for you to design like a pro. There are free circuit design software for you to download so you will be biased to a supplier's components. Then some other free software will turn your design into state of the art circuit boards. It's a little expensive to make a single product. But if you make a few to give it to family and friends, the cost isn't that bad.

Inevitably, I can't rely on cardboard boxes. They have to be replaced all the time. Again thanks to the Internet, you can use any materials you desire, from carbon fiber to metals to plastics. You just draw your parts on a free CAD package, push a button, and the price will be quoted to you. For my case acrylic is suitable. I can cut and glue it myself or I can find laser machines to cut the pieces for me with high precision.

If I go through with these, someday I may get rid of the bucket and turn the automatic waterer into a sculptured acrylic fountain.

Vacation automatic dog feeder for large breeds

The background is that I have just two days to find an automatic feeder so I can escape for a few days. Feeders are too expensive or not good enough to be sold in stores, so you can return easily. I couldn't find one and couldn't wait for mail order, so I have to build one. I don't even have time to wait for mail order components. And since I have no time to test the feeder, it must be very reliable.

For the first draft I can think of timer and sprinkler valves. For off the shelf components, I have to use one timer per day to activate something. Water is a good counter weight to bring food down from somewhere. Tubes can be custom made easily. Now sprinkler timers have 7 day program and each has at least alternate day programs. So I can save half the number of timers. I wasn't expecting too much of a vacation, just a weekend get away or up to a week will be good enough. It turn out that one timer per two days isn't a reality and so many custom pipes become a nightmare.

Then came the thought of a toy car coming out from somewhere to bring the food. A car each day. But now cars all come with remote control, so I have to rip off the remote control to get to the electronics, which adds to another level of unreliability. And also, the battery saving features in the cars may do something unexpected.

Fry's save the day. Now instead of an Outpost website, they put their name on it. I found toy motors online and found it in their stores too. Motors are everywhere, but theirs are kits, complete with gears box and mounting screws. Surprisingly it's purely made in Japan, and I don't know how they justify the low tech manufacturing, though the plastic gears are rather precise.

At the end, it become something like this, for each day:

• One AC 7 day timer - reliable and easy to program, you can't go wrong
• One AC to DC adaptor - to get 3 V for battery operated motor. With the exchangeable plugs, the motor wires can be clipped to the plugs without soldering.
• One motor with low gear ratio and mounted wheel.
• One heavy plank wood beam 1" x 2" in cross section
• A tray large enough for one portion of dog food
• Sewing thread to pull the tray
• A table in the yard
• Optionally a large bowl to receive the dog food

The motor is mounted at the end of the wood beam, which overhangs on the table. When the motor is on, it will coil the sewing thread and pull the tray of food. The tray is initially at the edge of the table, next to the beam as a sliding guide. Pulled by the motor at the end of the overhanging beam, the tray will fall off the table, and the food will fall down onto the ground or a huge bowl. Food pellets will fall everywhere due to the inaccurate trajectory of the tray. So you need a huge bowl to receive it or let it fall on the ground. You can also wrap the dog food in a bag if the bag is eatable or the dog will not eat it, you get the idea.

The gear ratio has to be low enough that the motor is powerful enough to overcome friction, and powerful enough to pull the thread to breaking point after the dog food is delivered to the ground. Since the thread is attached to the wheel and to the tray, the string thread has to break or it will be chaos. The mounted wheel isn't important as long as the thread has something to tie to. The powerful motor will ensure that the thread will coil up somewhere and pull the tray along the beam.

The beauty of it is the reliability. If anything fails the dog just miss one meal. Unlike the other feeders, the dog will starve for a week and die.

I have been thinking of improving it so it can be used daily to save labor. However, you need something like a grain screw as in the commercial feeders. If I can find something like that, I can attach it to an electric drill, which could be rather reliable. Though the amount of dog food delivered will not be exact.

There are also other toy motor kids that allow you to build a conveyor belt for example. You might be able to build a single feeding machine instead of 7 machine if you leave for a week. For reliability, you can use two machines, one for the even and one for the odd days.

Home Security - cam, monitor and DVR

The current mainstream setup is a wireless Wifi IP CAM at right, and a PC anywhere in the world where you want to monitor or record the video. The cheapest CAM is about $100. The security version with a metal housing can cost 10 times more.

You also need a Wifi router (<$40) to receive the video, a broadband modem and of course Internet connection. Off-site monitoring and recording is as secure as your telephone line (DSL) or cable TV line, which are pretty easy to find and cut depending on areas. Another disadvantage of this kind of system is that you need a PC, which is the obvious target to smash when intruders get through.

The other concepts are small portable self contained devices that can easily be hidden. They are easier to use than a camcorder and there's no need for installation. You can even bring it to a hotel!

The system on the left includes up to 4 wireless quarter sized cameras that can easily be hidden somewhere, and a palm sized monitor and recorder, which can also be hidden somewhere. For the less than $200 system, you can have multiple systems hidden in different places for redundancy.

Using SD cards, you can record several hours of DVD sized video. The system used to come with an 20GB internal hard drive, which will last about a day of continuous recordings. Using half sized resolution, which is still better looking than analog VCR systems, the record time will last for days.

The new systems come with a USB connection, which probably allows you to record video on an dirt cheap external hard drive. The old 40GB and 80GB that people throw away are about the same size. You only need to buy a few dollar adapter and you can record continuous for many days.

Even if you can record for days, you may want a security aware DVR system that don't need any attention, 24/7/52. The DVR at right works with any NTSC or PAL signal. Recording only starts if motions are detected on the images. The detection algorithms are primitive but the storage space is drastically reduced - even if you have a lot of moving tree branches, pets and wild animals etc.

The new videos or images override the old ones automatically. So if you have a large enough SD card, you know you always have a week of most current video stored in the device. A 4GB SD card can last you for months. The video quality is comparable or slightly better than VCR systems. The frame rate is low but typically much faster than time lapsed VCR systems.

The device is thin and palm sized. It's so compact and cheap (<$100) that you can just stick a tiny and cheap wired camera to it and hide the whole thing outside the door for example. That's even simpler than a wireless system. You can afford multiple units too. Instead of rotating the CAMS for recording, you can have one DVR for each CAM.

Night vision and motion detection
You don't really want a night vision cam alone because the video quality at dark will be poor even for military standards. Though a night vision cam can maintain video sync at total darkness with only a little faint red infrared LED illumination that usually comes with the cam. To record something decent you must add a low cost passive IR motion detector to trigger the flood lights for example. The switching of the lights will be seen as motion in the DVR with motion detection above.


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